The New Oxometallates Cs4[FeO3], Cs4[ZnO3] and Cs3[BO3] with Trigonal-planar Anions – Decomposition Products of Alkali Metal Suboxometallates

Three new cesium oxometallates with trigonal-planar [MO3]n− anions (M = Zn, Fe, B) were observed as products of reactions aimed at the formation of alkali metal suboxometallates A9MO4 (A = Rb, Cs; M = Al, Ga, In, Fe, Sc), or as decomposition products thereof. Cs4[FeO3], Cs4[ZnO3] and Cs3[BO3] crystallize with new structure types (Cs4[FeO3]: triclinic, space group P1̄, a = 7.0652(1), b = 7.125(1), c = 9.939(2) Å, α = 80.74(2), β = 71.32(2), γ = 64.04(2)◦, Z = 2, Cs4[FeO3]: monoclinic, space group P21/c, a = 7.146(4), b = 18.572(1), c = 7.050(4) Å, β = 115.47(4)◦ , Z = 4, Cs3[BO3]: orthorhombic, space group Pnma, a = 10.967(1), b = 10.967(1), c = 10.353(1) Å). In all structures the trigonal-planar anions have no or low point symmetry, but deviate only marginally from ideal 6̄m2 symmetry. The new crystal structures can be derived from simple and highly symmetrical packings of spheres or from known binary structure types.